How can I help this homeless girl ?

I’m a 20 year old girl and I study chemical engineering, so now we have a girl that works for us as a cleaning lady, she is 19 and homeless, she never mentioned her parents.She works everyday from 8am to 9:30pm. She can’t afford to go to college,she stays on the streets, I asked mom if she can stay at our place for... show more I’m a 20 year old girl and I study chemical engineering, so now we have a girl that works for us as a cleaning lady, she is 19 and homeless, she never mentioned her parents.She works everyday from 8am to 9:30pm. She can’t afford to go to college,she stays on the streets, I asked mom if she can stay at our place for a short period of time until she find a place to stay but mom refused, the girl is totally normal,she’s not an addict, she’s been working for us for months now and she haven’t stole anything! She’s very quite and shy,my mom yells at her sometimes she pays her late ,call her names and treats her very bad but she does not answer back or say anything, my mom doesn’t not pay her good and sometimes make her wait till the middle of the month or even skips some months! Mom says she’s homeless let her work her butt off for the money. I just feel bad for her because it’s very cold outside nowadays and her clothes are very light and worn out, her shoe is teard up and I don’t think she eats any proper meal! One day there was some leftover food from lunch, she asked my mother if she can have it but mom refused and threw it away !! I even asked my mom if she can have lunch or dinner with us at times but she refused as well ,because she hates the idea of her sitting with us on the same table and she said it’s family time and she shouldn’t be sitting with us , I told her she can eat alone in the kitchen but my mom said she is old enough to look after herself ! How canI help her?